Follow-up of patients with uncertain symptoms during an oral food challenge is useful for diagnosis.

BACKGROUND: Uncertain symptoms often emerge during an oral food challenge (OFC), and Open-OFCs with those uncertain mild symptoms are ordinarily regarded as positive. Double-blind placebo-controlled food challenges should be conducted to determine these associations. Nevertheless, studies regarding the diagnosis of uncertain food allergy symptoms are lacking. We examined the diagnostic decision for a food allergy based on uncertain symptoms during an Open-OFC.

METHODS: We conducted an Open-OFC between August 2005 and April 2012 with 2271 cases who suspected as allergic to hen's eggs, cow's milk, or wheat. For the primary diagnosis, Open-OFCs with obvious symptoms were classified as "positive," no symptoms as "negative," and uncertain, indeterminate symptoms as "uncertain." We encouraged the children in the uncertain group to consume the causative foods at home more than twice; if any definitive symptoms were induced, children were classified as "intolerant," and children without any symptoms were classified as "tolerant," for the final diagnosis.

RESULTS: We analyzed 454 uncertain cases excluding 781 positive cases and 1036 negative cases. The symptoms that occurred for the uncertain cases included slight abdominal pain, localized skin rash, and an isolated cough. Of these cases, 362 (79.7%) were considered tolerant at the final diagnosis. Of the intolerant children at the final diagnosis, the induced symptoms at home were not serious.

CONCLUSIONS: Monitoring of recurring symptoms following consumption of causative foods at home by patients with uncertain symptoms improves the diagnostic accuracy of an Open-OFC.